An enclosure defining a region (e.g., hotel rooms, offices, laboratories, buildings, cruise ships, airport terminals, and the like) may be sterilized by exposing the region (and any articles therein) to a sterilizing agent, such as vaporized hydrogen peroxide. Vaporized hydrogen peroxide may be generated by vaporizing a metered quantity of an aqueous solution of hydrogen peroxide (e.g., about 30% to 59% hydrogen peroxide, by weight). The vaporized hydrogen peroxide is carried into the region by a carrier gas (e.g., air). As used herein the term “sterilization” includes, but is not limited to, sterilization, disinfection, or sanitization, effecting lethal neutralization of biological contamination, including bio-warfare contamination.
The phases of a typical vaporized hydrogen peroxide treatment process include: a drying phase, a conditioning phase, a sterilization phase and an aeration phase. During the drying phase, the region is typically dried to a low humidity level using a dryer (e.g., a desiccant dryer). A conditioning phase follows the completion of the drying phase. During the conditioning phase, vaporized hydrogen peroxide is injected into the region at a relatively high rate to rapidly increase the hydrogen peroxide concentration within the region to an appropriate concentration level. After completion of the conditioning phase, the sterilization phase commences. During the sterilization phase, injection of the vaporized hydrogen peroxide is typically regulated to maintain a substantially constant hydrogen peroxide concentration within the region for a required exposure time. An aeration phase follows the completion of the sterilization phase. During the aeration phase, injection of vaporized hydrogen peroxide into the region is stopped and vaporized hydrogen peroxide is removed from the region until the vaporized hydrogen peroxide concentration is below an allowable threshold level (e.g., 1 ppm).
In certain applications it is advantageous and desirable during the aeration phase to reduce the concentration of vaporized hydrogen peroxide in the region to a level below 1 ppm in as short a time as possible (e.g., fewer than 2 hours), thereby allowing the region to be quickly returned to use. Accordingly, there is a need for a method and apparatus that can effectively and efficiently reduce large concentrations of vaporized hydrogen peroxide in a region to a concentration below the allowable threshold level.
Currently, a catalytic destroyer is often used to reduce the concentration of vaporized hydrogen peroxide by breaking down vaporized hydrogen peroxide into water vapor and molecular oxygen during the aeration phase. Such catalytic destroyers are beneficial in decomposing vaporized hydrogen peroxide concentrations that are above tens of parts per million. However, at low concentrations of vaporized hydrogen peroxide such catalytic destroyers are less efficient at decomposing vaporized hydrogen peroxide into water vapor and molecular oxygen. This may be especially problematic when the air carrying the vaporized hydrogen peroxide is forced through the catalytic destroyer at a high rate, thus reducing the residence time of contact between the elements of the catalytic destroyer (e.g., copper) and the vaporized hydrogen peroxide.
The present invention addresses these and other drawbacks of the prior art, and provides a method and apparatus that effectively and efficiently reduces large and small concentrations of vaporized hydrogen peroxide within a region.